182 Annals of the South African Museum. 



Unfortunately the sutures of the occiput are not clearly shown, 

 but some points in the structure can be discerned. The basi- 

 occipital condyle is large and rounded, and projects considerably 

 behind the occipital plate. The lateral margin of the foramen 

 magnum is formed by the exoccipital, which also forms the upper 

 margin of the foramen jugulare. The exoccipital is a larger bone 

 than that described by Watson in the Gorgonopsians Arctops and 

 Scymnognath'us. The two exoccipitals do not meet, but the upper 

 border of the foramen magnum is formed by the supraoccipital. 

 The post-temporal fossa is of moderate size, on a level with the 

 foramen magnum. The bone which forms almost the whole of 

 its upper border is, I think, the supraoccipital, which is very wide 

 and comparatively shallow. Superiorly there is a pronounced 

 horizontal backward extension of the squamosal, so that the 

 tabulare is hidden when the skull is viewed from above. This 

 bone, the limits of which I cannot determine, lies laterally to the 

 supraoccipital and forms part, at least, of the outer border of 

 the post-temporal fossa. In the Therapsida as far as it has hitherto 

 Ix-cn described it almost invariably extends down outside this 

 f<>ssa to meet the paroccipital process ; but the lower limit in 

 this form is indeh'nable. It is very doubtful, however, whether 

 the tabulare and the paroccipital process meet. The paroccipital 

 process is a stout, high bone forming the whole of the lower border 

 of the post-temporal opening. Externally it articulates for most 

 of its height with the squamosal. Internally it meets the ex- 

 occipital and the basioccipital. The extreme inner and front 

 corner of the bone forms part of the border of the fenestra ovalis. 

 The paroccipital process has a considerable forward extension 

 laterally, and the outer part of its under surface has a groove 

 ending in what is apparently a foramen between this bone and 

 the squamosal. 



The fenestra ovalis is a medium-sized hole, apparently not 

 bounded by bone on its outer side. Its outer posterior border is 

 formed by the paroccipital process, the anterior half of the border 

 is formed by the basisphenoid tuber and the prootic, and the 

 remainder by the basioccipital. It lies well in front of, and a 

 little below, the basioccipital process. 



Seen from below, the anterior part of the basioccipital between 

 the fenestrae ovales is strongly concave, and the median depression 

 is continued forward to the basisphenoid. Anteriorly it ends 

 abruptly and gives place to a deep and narrow median basisphenoid 



